1. Field of the Invention
Many different systems have a need for a source of microwave power having a certain frequency. Microwave sources employing negative-resistance diodes, filter circuits, and impedance matching circuits have been used as sources of microwave power due to their relative simplicity, small size and light weight. The invention relates to such a microwave power source.
2. Description of the Prior Art
Oscillator circuits employing two-terminal negative-resistance devices have been known for many years. IMPATT, TRAPATT, BARITT, and GUNN diodes are some of the negative-resistance devices used in oscillator circuits. These oscillator circuits have more recently been used in power combiners, where the power outputs of several oscillator circuits are combined to yield power levels higher than is obtainable from any one oscillator circuit.
A negative-resistance oscillator basically comprises a negative-resistance device connected through a resonator, tuned to the desired frequency, to a load having a positive resistance. The device impedance is equal to the negative of the transformed load impedance. To achieve optimum operational efficiency, an impedance-matching network is usually incorporated into the oscillator circuit.
Prior art oscillator circuits have used negative-resistance devices to feed oscillatory electromagnetic energy to a load. Typically, these circuits disposed the negative-resistance device at one end of a coaxial transmission line and disposed a dissipative impedance at the other end of the coaxial transmission line. A coupling circuit located between the negative-resistance device and the dissipative load coupled energy of the desired frequency to a resonant cavity. The energy was then coupled to an output transmission line and fed to an appropriate load.
These prior art oscillator circuits had certain disadvantages, including those related to the use of a waveguide short in combination with a coupling iris as the tuning mechanism. In this arrangement, the oscillatory energy was coupled to a resonant cavity or a standard rectangular waveguide. As a result, such prior art oscillator circuits suffered from narrow tuning ranges, narrow instantaneous injection bandwidths, and relatively low circuit efficiency.